Process For Preparing Porphyrin Derivatives, Such As Protoporphyrin (IX) And Synthesis Intermediates

ABSTRACT

The present invention relates to a process for preparing a porphyrin of formula (I), optionally in the form of a salt with an alkali metal and/or in the form of a metal complex: 
     
       
         
         
             
             
         
       
     
     in which:
         R and R′ are as defined in claim  1 ,
 
comprising:
   a step of condensation, in an acidic medium, between a dipyrromethane of formula (II):       

     
       
         
         
             
             
         
       
     
     in which R′b is as defined above for (I),
 
and a dipyrromethane of formula (III):
 
     
       
         
         
             
             
         
       
     
     in which R″ is as defined in claim  1 , and also the compounds of formula (III).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. provisionalapplication 60/943,735, filed Jun. 13, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel process for preparing porphyrinderivatives, such as protoporphyrin (IX), and also to intermediates forthe synthesis of these compounds.

2. Summary of the Related Art

Certain porphyrins are known and used for their biological or medicalproperties. By way of example, mention may be made of the followingporphyrins of formula:

-   -   in which:    -   Ra=—CH═CH₂, then named protoporphyrin IX,    -   Ra=—CH₂CH₃, then named mesoporphyrin,    -   Ra=—CH(OH)CH₃, then named hematoporphyrin,    -   Ra=H, then named deuteroporphyrin,    -   Ra=—CH₂CH₂COORb with Rb being a hydrogen atom or a methyl,        ethyl, n-propyl or i-propyl group, then named coproporphyrin        III,    -   Ra=—C(O)CH₃, then named diacetyldeuteroporphyrin.

These porphyrins can be used in the form of salts, for example of a saltwith an alkali metal at the two acid functions, such as a sodium salt.

It is also possible, depending on the applications, for these porphyrinsto be used in a complexed form, for example complexed with a metal suchas Fe, or alternatively a metal salt such as FeCl or FeOH. The complexof protoporphyrin IX with Fe is called heme, that with FeOH is calledhematin and that with FeCl is called hemin.

These porphyrins are most commonly prepared by hemisynthesis, whichposes the problem of impurities of animal origin, in particular, thatmay be present. For certain applications, for example in the case ofprotoporphyrin (IX), or of its sodium salt, which may be used in cellculture media, the desire is to provide a completely syntheticpreparation process which uses only products of synthetic origin.Certain processes of preparation by chemical synthesis of thesecompounds have already been proposed. The publications in J C S PerkinI, 1974, 1771-1781 and 1188-1194, for example, describe the preparationof protoporphyrin IX. A known method for preparing protoporphyrin, towhich reference is made in these publications, is referred to as theMacDonald process and consists in coupling, in the presence of a metalcation M⁺ such as Zn²⁺ or Fe³⁺, the following two pyrromethanes (A) and(B):

-   -   so as to give a porphodimethane structure (C):

-   -   which must subsequently be oxidized so as to form the metalated        porphyrin (D):

Such a method is in particular described in Science of SynthesisHouben-Weyl, vol. 17, 1081-1235 and in The porphyrin Handbook, vol. 1,synthesis and Chemistry, Academic Press, Boston, 2000.

It is subsequently necessary to demetalize the porphyrin, in thepresence of sulfuric acid, if said porphyrin must be used in free form.The latter step in particular is not quantitative and the porphyrinobtained does not have a satisfactory degree of purity. The high—C(O)CH₃ function must also be converted to —CH═CH₂.

SUMMARY OF THE INVENTION

In this context, the present invention proposes to provide a newsynthetic preparation process free of any contaminant of animal origin,which makes use of only products of synthetic origin, and which issuitable, in particular, for the synthesis of protoporphyrin IX, ofmesoporphyrin, of hematoporphyrin, of deuteroporphyrin, ofcoproporphyrins III and of diacetyldeuteroporphyrin, optionally in theform of salts. This process must in particular allow them to be producedwith high yields and a high degree of purity. The process according tothe invention must also be readily industrializable and show goodprofitability. The process developed in the context of the inventionmakes it possible, in addition, to prevent the intermediate formation ofa metalated porphyrin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this context, the invention relates to a process for preparing aporphyrin of formula (I), optionally in the form of a salt:

-   -   in which:        -   R is a hydrogen atom or a group selected from: —CH═CH₂,            —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a, with R′a            being a hydrogen atom or a methyl, ethyl, n-propyl or            i-propyl group,        -   R′ is a hydrogen atom or a group R′b selected from methyl,            ethyl, n-propyl or i-propyl,    -   comprising:        -   a step of condensation, in an acidic medium, between a            dipyrromethane of formula (II):

-   -   in which R′b is as defined above for (I),    -   and a dipyrromethane of formula (III):

-   -   in which R″ is selected from hydrogen, —CH═CH₂, —CH₂—CH₃,        —CH(OH)CH₃, —C(O)CH₃, —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃ and —CH₂CH₂Cl        or —CH₂CH₂COOR′a, wherein R′a is hydrogen, methyl, ethyl,        n-propyl, or i-propyl, and R″ is either identical to    -   R as defined above for (I) or is a precursor of R, so as to form        the porphyrin of formula (I′):

-   -   in which R″ and R′b are as defined above for (II) and (III),    -   and:        -   when R″ is a precursor of R, further comprising converting            R″ to R, and        -   when R′═H, further comprising eliminating R′b so as to form            —COOH moieties, optionally in the form of a salt.

The process according to the invention makes it possible to obtainporphyrins that have a satisfactory solubility, in particular in anaqueous solution. A subject of the present invention is also theporphyrins of formula (I):

-   -   in which:        -   R is a hydrogen atom or a group selected from: —CH═CH₂,            —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a, with R′a            being a hydrogen atom or a methyl, ethyl, n-propyl or            i-propyl group,        -   R′ is a hydrogen atom or a group R′b selected from methyl,            ethyl, n-propyl or i-propyl,    -   and also the salts thereof that can be obtained according to the        process of the invention.

By way of example of salts with porphyrins of formula (I), mention may,for example, be made of salts with an organic or inorganic base. Inparticular such salts may be formed with the porphyrins of formula (I)which comprise a carboxylic acid function; it is preferably an alkalimetal salt, in particular a sodium, potassium or lithium salt, or anammonium salt, an organic amine salt or a salt of an amino acid such asarginine or lysine.

It is also possible to form salts of the porphyrins of formula (I) withan inorganic or organic acid, which enable, for example, a suitableseparation or crystallization of the compounds of formula (I), and alsopharmaceutically acceptable salts. As appropriate acid, mention may bemade of: picric acid, oxalic acid or an optically active acid, forexample a tartaric acid, a dibenzoyltartaric acid, a mandelic acid or acamphosulfonic acid, and those which form physiologically acceptablesalts, such as the hydrochloride, hydrobromide, sulfate, hydrogensulfate, dihydrogen phosphate, maleate, fumarate, 2-naphthalenesulfonateor para-toluenesulfonate.

The salts of the compounds of formula (I) are prepared according totechniques well known to those skilled in the art, by incorporating thecorresponding step of formation of the desired salt, through the actionof the corresponding base or acid, preferably in a final step, into theprocess according to the invention.

The process according to the invention is illustrated in SCHEME 1hereinafter, in which R, R″ and R′b are as defined for the compounds offormulae (II), (III) and (I).

Depending on the nature of the group R, the coupling can be carried outbetween a compound (II) and a compound (III) in which R″═R: this is, forexample, the case when R═H, —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ or—CH₂CH₂COOR′a, with R′a being a hydrogen atom or a methyl, ethyl,n-propyl or i-propyl group.

If the group R′b=R′, the compound (I′) directly obtained after thecondensation step is the desired compound (I), without any additionalstep being necessary. If the compound R′b is other than R′, which is thecase when R′═H or else in cases where the acid functions are in the formof a salt, for example, with an alkali metal such as Na⁺ or K⁺, thecoupling is followed by deprotection of the acid function by eliminationof the group R′b, in order to convert the compound (I′) to compound (I).

The coupling can also be carried out with a compound (III) in which R″is a precursor of R (also referred to herein as a group that isprecursor of R). The expression “precursor of R” and “group that is aprecursor of R” are intended to mean a group which, after one or morechemical reactions, gives the desired group R. By way of example of suchprecursor groups, in particular for the —CH₂═CH₂ group, mention may, forexample, be made of the —C(O)CH₃, —CH(OH)CH₃, —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃or —CH₂CH₂Cl groups, —C(O)CH₃ and —CH(OH)CH₃ groups being particularlypreferred. The coupling with the compound (III) gives a compound (I′):

in which R″ is a group that is a precursor of R. The group that is aprecursor of R must then be converted so as to give the desired group R,in one or more steps. This is, for example, the case for the preparationof the compounds of formula (I) in which R=—CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃or H. In the case of such groups, one of the methods consists incarrying out the coupling with a compound (III) in which R″=—C(O)CH₃,which is subsequently converted, after the step of condensation betweenthe compounds (II) and (III), so as to obtain the desired group R.

Moreover, depending on the nature of the group R′, the coupling can becarried out between a compound (III) and a compound (II) in whichR′═R′b. On the other hand, in the case where R′═H, or else in caseswhere the acid functions are in the form of a salt, for example, with analkali metal such as Na⁺ or K⁺, the coupling is followed by deprotectionof the acid function by elimination of the group R′b.

When, after the step of coupling between the compounds (II) and (III),the two steps, i.e. the conversion of the groups R″ to R and theelimination of the groups R′b, are necessary, the deprotection of theacid function can take place before or after the conversion of thegroups R″ to R. It is, however, preferable to eliminate the groups R′bafter the conversion of the group R″ to R, since ester functions improvethe solubility in the reaction solvents.

Unlike the MacDonald method of the prior art, the step of condensationbetween the compounds (II) and (III) is carried out in the absence ofmetal, salt or metal derivative, liable to complex with the porphyrin(I′) formed.

In the context of the invention, for the preparation of a compound offormula (I) in which R is a hydrogen atom or a group selected from:—CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a with R′a being ahydrogen atom or a methyl, ethyl, n-propyl or i-propyl group, thecoupling may be carried out either with a compound (III) in which R″ isthe final group R, or with a compound (III) in which R″ is a group thatis a precursor of the final group R.

For the preparation of a compound of formula (I) in which R is a —CH═CH₂group, use will preferably be made of:

-   -   a step of condensation, in an acidic medium, between a        dipyrromethane of formula (II):

-   -   in which R′b is as defined above for (I),    -   and a dipyrromethane of formula (III):

-   -   in which R″ is a group that is a precursor of R, for example a        —CH(OH)CH₃ or —C(O)CH₃ group,    -   followed by conversion of the groups R″ to R,    -   and when R′═H, by elimination of the groups R′b so as to form a        —COOH groups, optionally in the form of a salt.

The process according to the invention is particularly suitable for thesynthesis of protoporphyrin and of salts thereof, in particular itssodium salt of formula (IC.2, 2Na):

In the case of the preparation of a compound of formula (IC):

-   -   in which R′ is as defined for (I), or a salt thereof, for        example, with an alkali metal, a coupling is advantageously        carried out between a pyrromethane of formula (II):

-   -   in which R′b is as defined for (I), and is preferably a methyl        group,    -   and a dipyrromethane of formula (IIIa):

-   -   so as to form the compound of formula (Ia):

-   -   in which R′b is as defined for (I), and is preferably a methyl        group,    -   followed        -   by reduction of the —C(O)CH₃ function, resulting in the            formation of the porphyrin of formula (Ib):

-   -   in which R′b is as defined for (I), and is preferably a methyl        group,        -   followed by an elimination reaction that converts the groups            —CH(OH)CH₃ to —CH═CH₂,        -   and, in the case where R′ is a hydrogen atom, by a step of            deprotection of the —COOH function by hydrolysis,    -   or, in the case where the compound (IC) that it is desired to        form is in the form of a salt with an alkali metal, by a        saponification step.

It should be noted that, in the context of the invention, the compoundof formula (Ib) comprises two asymmetrical carbons and can be in theform of a mixture of isomers or of a pure isomer.

This process for preparing the compounds of formula (IC) is illustratedin SCHEME 2 below in which R′b is as defined for the compounds offormula (II):

-   -   in which R′═R′b

In the case of the preparation of protoporphyrin IX in the form of thesodium salt of formula (IC.2, 2Na):

the last step of the process consists of the saponification of the two—COOR′b groups of the compound of formula:

in which R′b is as defined for (I), and is preferably a methyl group.This saponification step can be carried out by the action of sodiumhydroxide, in the presence of methanol. For example, the saponificationstep is carried out in dichloromethane at reflux. According to anunpreferred variant, it could also be envisaged that this saponificationstep be carried out after the coupling between the compounds (II) and(IIIa), but before the desired —CH═CH₂ group is obtained.

The condensation reaction between the two pyrromethanes (II) and (III)or (IIIa) is preferably carried out in the presence of an acid selectedfrom the carboxylic acids, trifluoroacetic acid, hydrochloric acid,trichloromethanesulfonic acid, methanesulfonic acid,trifluoromethanesulfonic acid, tetrafluoroboric acid, hydrobromic acidand hydriodic acid. The acid is preferably a strong acid, preferablytrifluoroacetic acid or trichloromethanesulfonic acid. The acid ispreferably used in excess relative to the pyrromethane (II), for example2 mol equivalents of acid per mol equivalent of pyrromethane (II).

Advantageously, the condensation reaction between the two pyrromethanes(II) and (III) or (IIIa) is carried out in the presence of a desiccatingagent, intended to take up water molecules. By way of desiccating agent,mention may be made of anhydrides, molecular sieves and sulfuric acid,acetic anhydride being preferred. In the case of the use of aceticanhydride, the latter is preferably present in an excess, for example,of at least 10, preferably of at least 50 mol equivalents relative tothe pyrromethane (II) (or per one mol equivalent of pyrromethane (II)).

It will also be advantageous to carry out the condensation withsubstantially one equivalent or a slight excess of pyrromethane (II),relative to the pyrromethane (III) or (IIIa). By slight excess, it ismeant that the condensation between pyrromethane (II) and pyrromethane(III) or (IIIa) is carried out at a molar ratio between these twocomponents of 1:1.2, or preferably of 1:to 1.1.

The condensation reaction between the two pyrromethanes (II) and (III)or (II) and (IIIa) is, for example, carried out at a temperature of from10 to 50° C., preferably from 20 to 25° C., in a protic solvent, such asacetic acid.

The reactions following the coupling, that make it possible to obtainthe desired group R, make use of known methods.

The elimination reaction that converts the groups —CH(OH)CH₃ to —CH═CH₂is advantageously carried out in the presence of an acid halide,preferably an acid chloride such as benzoyl chloride. For example, theelimination reaction that converts the groups —CH(OH)CH₃ to —CH═CH₂ iscarried out in an aprotic polar solvent such as DMSO (dimethylsulfoxide), acetone or preferably DMF (dimethyl formamide), preferablyat a temperature of from 50 to 200° C. for a period of 30 minutes to 3hours, and preferably at a temperature of from 80 to 120° C. for aperiod of the order of one hour.

The reduction of the —C(O)CH₃ function to —CH(OH)CH₃ is advantageouslycarried out in the presence of a hydride, preferably a borohydride suchas NaBH₄ or BH₃. Preferably, the reduction of the —C(O)CH₃ function iscarried out in dichloromethane in the presence of methanol, for exampleat a temperature of between 0 and 60° C., preferably between 20 and 30°C.

Subsequently, the compound of formula (I) in which R=—CH═CH₂ can besubjected to other chemical reactions, in order to obtain other groupsR. The compound of formula (I) in which R=—CH₂—CH₃, for example, can beobtained from the corresponding compound of formula (I) in whichR=—CH═CH₂ by catalytic hydrogenation. For example, use may be made ofthe technique described in Tetrahedron Letters 2006, 47(29), 5119-22,which uses a RuCl₃ catalyst in AcNMe₂ at a temperature of the order of80°.

Similarly, the compound of formula (I) in which R═H can be obtained fromthe corresponding compound of formula (I) in which R=—C(O)CH₃, byintermediately forming the compound of formula (I) in whichR=—CH(OH)CH₃, which is subsequently deacetylated by the action of BF₃ inthe presence of HS—(CH₂)₂—SH, for example using the method described inJOC, 1983, 48(24), 4779-81 or J. Chem. Soc, Chemical Communications,1981, (6), 253-4.

According to one of its variants, the process according to the inventioncan therefore be implemented for the preparation of the compounds offormula (IA):

-   -   in which R′ is as defined for (I), or a salt thereof, for        example, with an alkali metal,    -   by coupling the pyrromethane of formula (II):

-   -   in which R′b is as defined above for (I), and is preferably a        methyl group,    -   with a dipyrromethane of formula (IIIa):

-   -   followed, in the case where R′ is a hydrogen atom, by a step of        deprotection of the —COOH groups by hydrolysis,    -   and/or, optionally in the case where it is desired to form the        compound (Ia) in the form of a salt with an alkali metal, by a        saponification step.

The process according to the invention can also be implemented for thepreparation of the compound of formula (IB):

-   -   in which R′ is as defined for (I), or a salt thereof, for        example, with an alkali metal,    -   by coupling the pyrromethane of formula (II):

-   -   in which R′b is as defined above for (I), and is preferably a        methyl group,    -   with a dipyrromethane of formula (IIIa):

-   -   so as to form a compound of formula (Ia):

-   -   in which R′b is as defined above for (I), and is preferably a        methyl group,    -   followed by reduction of the —C(O)CH₃ function, so as to form        the —CH(OH)CH₃ function,    -   and, in the case where R′ is a hydrogen atom, by a step of        deprotection of the —COOH function by hydrolysis,

and/or, in the case where it is desired to form a compound (IB) in theform of a salt with an alkali metal, by a saponification step.

The compound (II) in which R′b=Me is a known compound, just like thecompounds (II) in which R′b is an ethyl or propyl group (J C S Perkin I,1974, 1188-1194 and 1771-1781). For their synthesis, reference may, forexample, be made to Austral. J. Chem. 1969, 22, 229, J C S, Chem. Comm.1985, (8), 470-1, Org. Bioorg. Chem. (1972-1999), 1987, (2), 265-76, andJ. Porphyrins and Phtalocyamines, 2002, 6 (9+10), 607-16.

On the other hand, the pyrromethanes of formula (III):

in which R″ is a group R selected from a hydrogen atom or a groupselected from: —CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and—CH₂CH₂COOR′a, with R′a being a hydrogen atom or a methyl, ethyl,n-propyl or i-propyl group, are new compounds and are an integral partof the invention.

Among the compounds of formula (III), mention may be made of those inwhich R″ is a group that is a precursor of —CH═CH₂ selected from:—C(O)CH₃, —CH(OH)CH₃, —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃ and —CH₂CH₂Cl.

The conversion of the —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃ or —CH₂CH₂Cl group to—CH═CH₂ is carried out according to the usual methods of eliminationwell known to those skilled in the art. For example, the —CH₂CH₂Cl groupcan be treated by the action of alcoholic potassium hydroxide asdescribed in J. C. S. Perkin 1, 1974, 1771-1781.

By way of example of such compounds, mention may be made of thepyrromethane of formula (IIIa):

The compounds (III) can be prepared according to SCHEME 3 hereinafter:

In the case where R″ is a —C(O)CH₃ group, the compound (IX) is, forexample, prepared by reaction of trimethylsilylpropyne and acetylchloride, in the presence of aluminum trichloride.

The coupling between the compounds (VII) and (VI) is preferably carriedout in an acidic medium, for example in the presence of TFA, HCl,MeSO₃H, SnCl₄ or HBF₄, and advantageously in the presence of HBF₄ or ofCF₃SO₃H. For example, the coupling is carried out in a solvent such asacetic acid, or preferably dichloroethane, for example at a temperatureof between 50 and 150° C., in particular of the order of 90 to 100° C.,for 1 to 12 hours.

The production of the compound (IV) by debenzylation of the compound (V)is, for example, carried out by catalytic hydrogenation. By way ofillustration, a metal catalyst, such as a nickel-based, platinum-basedor preferably palladium-based catalyst, can be used.

The following compounds of formulae (VIIa), (Va), (IVa) (compounds VII,V and IV, respectively, in which R″=—C(O)CH₃):

-   -   are also novel intermediates that are an integral part of the        invention.

For the preparation of the compound (IV) in which R″=—CH₂CH₂COOR′a withR′a as defined for (I), reference may be made to J C S, Perkin Trans 1Org and Bioorg Chem. 1987 (2), 299-305. The compound (IV) in whichR″=—CH₂CH₃ is, for its part, described in Zhurnal Obshcheikhimii 1966,36(7), 1208-10.

The present invention also relates to a process for preparing aporphyrin of formula (I), optionally in the form of a salt:

-   -   in which:        -   R is a hydrogen atom or a group selected from: —CH═CH₂,            —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a, with R′a            being a hydrogen atom or a methyl, ethyl, n-propyl or            i-propyl group,        -   R′ is a hydrogen atom or a group R′b selected from methyl,            ethyl, n-propyl or i-propyl,    -   in the form of a metal complex, for example iron, gallium,        nickel, zinc, palladium, cobalt, calcium or magnesium, in which        a step of complexation of a porphyrin, formed after the step of        condensation between the compounds (II) and (III) or (IIIa), is        carried out, by the action of the selected metal or of a metal        derivative or salt of the selected metal.

Such complexes correspond, in particular, to the following formula (I″):

-   -   in which:        -   R is a hydrogen atom or a group selected from: —CH═CH₂,            —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a, with R′a            being a hydrogen atom or a methyl, ethyl, n-propyl or            i-propyl group,        -   R′ is a hydrogen atom or a group R′b selected from methyl,            ethyl, n-propyl or i-propyl, and        -   Met is a divalent metal M(II) or a metal salt of a trivalent            metal M(III)X, with X being Cl or OH and M being iron,            gallium, nickel, zinc, palladium, cobalt, calcium or            magnesium.

The porphyrin of formula (I) or the porphyrin of formula (I′) obtained,in the process according to the invention, can be reacted with a metalor a metal salt or the hydroxide metal of the type chloride, hydroxide,acetate or sulfate in particular, the metal being, for example, chosenfrom iron, gallium, nickel, zinc, palladium, cobalt, calcium ormagnesium, so as to obtain the porphyrin of formula (I) in the form of ametal complex. This metalation necessarily takes place after thecoupling of the pyrromethanes (II) and (III) or (IIIa).

The complexation step is preferably carried out as a final step, on theporphyrin of formula (I), optionally in the form of a salt. For theformation of such complexes, reference may be made to the followingpublications, which describe the formation of metal complexes in thecase where R″ is a —CH═CH₂ group, or to known methods of complexationfor obtaining heme, hemin and hematin, these methods being adapted tothe various groups R and R′ as defined for all the compounds of formulaI:

Journal of Photochemistry and Photobiology, A: Chemistry, 172(1), 55-61,2005, which describes the formation of the following complex:

by the action of GaCl₃, followed by hydrolysis with potassium hydroxidein methanol, it being possible for this method to be adapted in asimilar manner to the formation of hematin, by the action of FeCl₃,

Journal of Molecular Catalysis A: Chemical, 235(1-2), 185-193, 2005,which describes the formation of the following complex:

by the action of Ni(OAc)₂, in DMF.

Journal of Molecular Catalysis A: Chemical, 235(1-2), 185-193, 2005,which describes the formation of the complex C:

by the action of Zn(OAc)₂, in a methanol/trichloromethane mixture.

Faming Zhuanli Shenqing Gongkai Shuomingshu, 1418885, which describesthe formation of the following complex:

by treatment with sulfuric acid, and then treatment with FeSO₄ followedby treatment with sodium hydroxide.

-   -   Tetrahedron Letters, 27(30), 3521-4, 1986, which describes the        formation of the following complex:

by the action of BF₄ ⁻, Ph₂S⁺(CH₂Ph) in dichloromethane, followed by theaction of PdCl₂ in the case where M=Pd, of NiCl₂ in the case where M=Ni,or of CoCl₂ in the case where M=Co, in methanol.

Journal of Organic Chemistry, 51(24), 4660-7, 1986, and Journal ofOrganic Chemistry, 51(5), 666-71, 1986, which describes the formation ofthe following complex:

by the action of FeCl₂, in a dichloromethane/acetonitrile mixture underan inert atmosphere.

The examples and preparations hereinafter make it possible to illustratethe invention.

SCHEME 4 hereinafter summarizes the various compounds prepared and thesteps of the process used in the preparations and examples.

The following abbreviations are used.

Bn=benzyl, Et=ethyl, Ac=—C(O)Me, Me=methyl

Preparation 1

Synthesis of the Pyrrole of Formula (3):

a) Preparation of the Compound of Formula (6):

A 4.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withethanol (2 l). At ambient temperature, sodium (2.2 g) is graduallydissolved so as to give a clear solution which is cooled to 0° C. Acetylacetonate (500.0 g, 5.0 mol) is added dropwise in 10 min, which resultsin gas being given off. 430 g of methyl acrylate are added dropwise tothe light yellow solution at 0° C. in 10 min, which results in gas beinggiven off. The reaction mixture is heated to ambient temperature and isthen refluxed for 1 h. The conversion is followed by HPLC. The mixtureis cooled to ambient temperature. Acetic acid (3 ml) is added and theethanol is eliminated by distillation under reduced pressure. Thedistillation of the crude mixture (95-105° C., 2.5 mbar) gives a lightyellow solution (747.8 g, 80%). The ¹H NMR analysis shows that the crudeproduct is an ˜1/1 mixture of compound (6) and of methyl 5-oxohexanoate.

b) Preparation of the Compound of Formula (5):

A 4.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withacetic acid (1.30 l) and refluxed. A solution of a mixture of compound(6) (248.71 g, 1.34 mol) and of dimethyl aminomalonate hydrochloride(367.50 g, 1.74 mol) in acetic acid (0.85 l) is added dropwise to themixture at reflux, over 1 h. The mixture is again refluxed for 2.5 h.The conversion is followed by HPLC. The reaction mixture is cooled toambient temperature and the acetic acid is eliminated by distillationunder reduced pressure. The dark crude product is triturated with water(4.5 l), which is added slowly, portionwise. The mixture is mechanicallystirred for a further 1 h and is then filtered, and the filtration cakeis washed with water (1 l). The recrystallization of the dark gray crudeproduct is carried out from ethanol/water (350/350 ml) by refluxing andthen cooling to 10° C. The precipitate is isolated by filtration andwashed with ethanol/water (4×100/100 ml). The product is dried underreduced pressure at ambient temperature, to give the compound (5) (95.00g, 28%) in the form of a light purple-colored solid.

¹H NMR (300 MHz, CDCl₃): 1.34 (t, CH₃), 2.21 (s, CH₃), 2.27 (s, CH₃),2.43 (t, CH₂), 2.70 (t, CH₂), 3.66 (s, CH₃), 4.29 (q, CH₂), 8.60 (broadsinglet, NH₂).

c) Preparation of the Compound of Formula (4):

A 2.5 l Keller round-bottomed flask equipped with a refluxcondenser/distillation head, a thermometer, a dropping funnel and anargon conduit is loaded with a solution of compound (5) (95.00 g, 0.38mol) in benzyl alcohol (685 ml) and heated to 120° C., which results inthe azeotropic removal of minor amounts of water. The mixture is thenheated to 190° C. The dropping funnel is loaded with a separatelyprepared solution of sodium (3 g) in benzyl alcohol (70 ml). Thissolution is added in 5 ml portions, which results in a vigorous refluxof the reaction mixture. The resulting methanol and ethanol are removedby semi-continuous distillation. The conversion is followed by HPLC. Thereaction mixture is cooled to 150° C. and then transferred into amixture of methanol (0.85 l), water (0.54 l) and acetic acid (10 ml). At30° C., crystallization takes place rapidly. The mixture is stirredagain at ambient temperature for 1 h. The product is isolated byfiltration. The product is dried under reduced pressure, to give thecompound (4) (113.30 g, 77%) in the form of an off-white solid.

¹H NMR (300 MHz, CDCl₃): 2.16 (s, CH₃), 2.27 (s, CH₃), 2.47 (t, CH₂),2.71 (t, CH₂), 4.70 (s, CH₃), 5.08 (s, CH₂), 5.28 (s, CH₂), 7.40 (m,10H), 8.60 (broad singlet, NH₂).

d) Preparation of the Compound of Formula (3):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with asolution of sodium (2.8 g) in methanol (710 ml). At ambient temperature,a solution of compound (4) (111.00 g, 0.28 mol) in THF (430 ml) is addeddropwise in 10 min. The mixture is stirred for a further 1 h. Theconversion is followed by HPLC. After the addition of acetic acid (7ml), the volatile products are removed under reduced pressure. The crudeviscous product is dissolved in ethanol (490 ml) and water (280 ml) isadded. The resulting mixture is stirred for 1 h at 0° C. and theprecipitated product is isolated by filtration. The product is washedwith ethanol/water (250/250 ml) and dried under reduced pressure, togive the compound (3) (53.31 g, 60%) in the form of a white solid.

¹H NMR (300 MHz, CDCl₃): 2.25 (s, CH₃), 2.31 (s, CH₃), 2.45 (t, CH₂),2.71 (t, CH₂), 3.67 (s, CH₃), 5.30 (s, CH₂), 7.40 (m, 5H), 8.60 (broadsinglet, NH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 2 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 8.53 min (>98%)

Preparation 2

Preparation of the Compound of Formula (VIII.1):

A 2.5 l Keller round-bottomed flask equipped with a refluxcondenser/distillation head, a thermometer, a dropping funnel and anargon conduit is loaded with a solution of ethyl4-acetyl-3,5-dimethylpyrrole-2-carboxylate (commercial product, AlphaAesar, Karlsruhe, Germany, product No. A 17365) (146.00 g, 0.70 mol) inbenzyl alcohol (1.00 l) and heated to 120° C., which results in theazeotropic removal of minor amounts of water. The mixture is then heatedto 190° C. The dropping funnel is loaded with a separately preparedsolution of sodium (2 g) in benzyl alcohol (20 ml). This solution isadded in 5 ml portions, which results in a vigorous reflux of thereaction mixture. The resulting methanol and ethanol are removedsemi-continuously by distillation. The conversion is followed by HPLC.The reaction mixture is cooled to 150° C. and then transferred into amixture of methanol (0.96 l), water (0.66 l) and acetic acid (12 ml).The mixture is cooled to −10° C. and again stirred at this temperaturefor 1.5 h. The precipitated product is isolated by filtration. Theproduct is dried under reduced pressure, to give the compound (VIII.1)(124.40 g, 65%) in the form of an off-white solid.

¹H NMR (300 MHz, CDCl₃): 2.34 (s, CH₃), 2.40 (s, CH₃), 2.52 (s, CH₃),5.23 (s, CH₂), 7.85 (m, 5H), 9.55 (broad singlet, NH)

Preparation 3

Preparation of the Compound of Formula (VI.1):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withcompound (VIII.1) (66.84 g, 0.25 mol), acetic acid (1.25 l) and sodiumacetate (73.90 g, 1.51 mol). In order to obtain a clear solution, themixture is heated to 35° C. and then cooled to ambient temperature.Sulfuryl chloride (32.4 ml, 0.40 mol) is added in 2 h, while thereaction is carefully controlled toward the end of the addition, inorder to minimize by-product formation due to overreaction. Additionalamounts of sodium acetate (50.0 g) are added, at ambient temperature,and the mixture is again stirred at ambient temperature overnight. Water(500 ml) is added, to give a clear solution. After the addition of a 9-lwater-methanol mixture (4.5 l), the reaction mixture is again stirred atambient temperature for 1 h with precipitation of the product. Theproduct is isolated by filtration and dissolved by refluxing in ethylacetate (220 m). The two-phase mixture is removed from the oil bath andmethanol (200 ml) is added with stirring. After further stirring for 1 hat ambient temperature, the product begins to crystallize. Additionalamounts of methanol (500 ml) are added and the mixture is stirred andcooled to −10° C. The product is isolated by filtration. The product isdried under reduced pressure, to give the compound (VI.1) (37.14 g, 45%)in the form of a white solid.

¹H NMR (300 MHz, CDCl₃): 2.07 (s, CH₃), 2.41 (s, CH₃), 2.53 (s, CH₃),5.27 (s, CH₂), 5.31 (s, CH₂), 7.32 (m, 5H), 9.40 (broad singlet, NH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 2 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 7.89 min (>94%)

Preparation 4

Preparation of the Compound of Formula (7):

a) Preparation of the Compound of Formula (9):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withglycine (80.00 g, 1.07 mol), benzyl alcohol (700 ml) andp-toluenesulfonic acid monohydrate (241 g, 1.27 mol). The thick whitemixture is heated to 100° C., which results in the formation of a clearsolution. The mixture is again stirred at 100° C. for 5 h. The mixtureis cooled to ambient temperature. Diethyl ether (4 l) is added slowly,which results in precipitation of the product. The product is isolatedby filtration, washed with ether (3×0.3 l) and dried under reducedpressure at 60° C. Because the conversion is incomplete, the white solidis taken up in toluene (2.3 l), and benzyl alcohol (0.3 l) andp-toluenesulfonic acid monohydrate (20 g) is added. The mixture isrefluxed for 4 h, while the water is continuously removed by means of aDean-Stark apparatus. The mixture is cooled to ambient temperature.Diethyl ether (1 l) is added slowly and the mixture is cooled to 0° C.,which results in precipitation of the product. The product is isolatedby filtration, washed with ether (3×0.3 l) and dried under reducedpressure at 60° C., to give the compound (9) (303.20 g, 84%) in the formof a white crystalline product.

¹H NMR (300 MHz, DMSO-D₆): 2.28 (s, CH₃), 3.90 (s, CH₂), 5.25 (s, CH₂),7.15 and 7.39 (AB, 4H), 7.37 (m, 5H).

b) Preparation of the Compound of Formula (8):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withmethyl formate (700 ml), compound (9) (303.0 g, 898.0 mmol) andtriethylamine (137 ml, 1 mol). The mixture is refluxed for 22 h. Theconversion is followed by HPLC. The heterogeneous mixture isconcentrated under reduced pressure, to give an oil (429 g). The productis dissolved in dichloromethane (1.5 l), washed with bicarbonate (2×0.5l) and water (0.5 l). The combined aqueous phase is re-extracted withdichloromethane (0.5 l). The combined organic phase is dried (Na₂SO₄),filtered and concentrated under reduced pressure (40 mbar, 45° C., 1 h),to give the compound (8) (149.2 g, 86%) in the form of an orangey yellowoil.

¹H NMR (300 MHz, CDCl₃): 4.12 (d, CH₂), 5.19 (s, CH₂), 6.33 (broadsinglet, NH), 8.23 (s, CHO).

c) Preparation of the Compound of Formula (7):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (8) (129.7 g, 671.3 mmol) and dichloromethane (1). The mixtureis cooled to 0° C. Triethylamine (234 ml, 1678 mmol) is added to give ayellow solution. POCl₃ (102.9 g, 671.3 mmol) is added in 50 min, whilethe temperature is maintained at between 0 and 5° C. The mixture isstirred for a further 2 h while it is heated to ambient temperature. Asolution of K₂CO₃ (134 g) in water (600 ml) is added slowly andcarefully in small portions at between 25 and 30° C. After completeaddition, the mixture is stirred for a further 1 h. Water (1 l) is addedand the phases are separated. The organic phase is washed with water(0.2 l). The combined aqueous phase is re-extracted with dichloromethane(0.5 l). The combined organic phase is dried (Na₂SO₄), filtered andconcentrated under reduced pressure, to give a brown oil (180 g).Chromatography is carried out on silica (500 g), elution being carriedout with dichloromethane. The fractions containing the product arecombined and concentrated under reduced pressure, to give anorangey-yellow oil. Storage at −10° C. allows crystallization of thecompound (7) (101.9 g, 87%) so as to form a stable product.

¹H NMR (300 MHz, CDCl₃): 4, 22 (s, CH₂), 5.23 (s, CH₂), 7.38 (s, 5H).

Preparation 5

Preparation of the Compound of Formula (IX.1):

A 4.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withaluminum trichloride (297.00 g, 2.23 mol) and dichloromethane (2.3 l)and cooled to 0° C. A solution of trimethylsilylpropyne (250.00 g, 2.23mol) and acetyl chloride (0.16 l, 2.23 mol) in dichloromethane (0.4 l)was added to the light yellow suspension in 1.5 h, the temperature beingmaintained at between 0 and 5° C. The brown solution with a certainamount of precipitated salt is heated to ambient temperature. Theresulting reddish-brown solution is poured into ice/water (2 l). Thelayers are separated and the aqueous phase is extracted withdichloromethane (0.5 l). The combined organic phase is washed with water(0.5 l), dried (Na₂SO₄), filtered and concentrated under reducedpressure, to give a greenish-black liquid (558 g). The product isdistilled at 180 mbar, to give a fraction (˜160 g) that boils between 64and 70° C. This product is again distilled at 210 mbar, to give thecompound (IX.1) (90.30 g, 49%) in the form of a colorless liquid thathas a boiling point of between 81 and 85° C.

¹H NMR (300 MHz, CDCl₃): 2.02 (s, CH₃), 2.31 (s, CH₃).

Preparation 6

Preparation of the Compound of Formula (VII.1):

A 1 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loadedsuccessively with the compound (7) (101.90 g, 0.58 mmol), dioxane (0.5l) and the compound (IX.1) (52.53 g, 0.64 mol). Whenmethyldiphenylphosphine (38.4 g, 0.19 mol) is added, the reactionbecomes highly exothermic.

The reaction mixture becomes dark and is heated at 100° C. for 1 h. Theconversion is followed by HPLC. The volatile products are removed underreduced pressure. The crude brown oil (209 g) is purified bychromatography on silica (2.1 kg), elution being carried out with atoluene/ethyl acetate (8/1) mixture. The fractions containing the pureproduct are combined and the volatile products are removed under reducedpressure, to give the compound (VII.1) (73.49 g, 49%) in the form of alight brown syrupy oil.

¹H NMR (300 MHz, CDCl₃): 2.13 (s, CH₃), 2.54 (s, CH₃), 5.32 (8 s, CH₂),6.68 (d, CH), 7.38 (m, 5H), 9.20 (broad singlet, NH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 2 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 7.55 min (>91%)

Preparation 7

Preparation of the Pyrromethane of Formula (2):

A 4.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (3) (52.0 g, 165.0 mmol) and diethyl ether (1.5 l). A freshlyprepared solution of bromine (11.0 ml, 214.0 mmol) in diethyl ether (0.5l) is added dropwise in 20 min at ambient temperature, so as to producean orangey-brown solution. The conversion is followed by HPLC. Ifnecessary, additional amounts of bromine are added. The mixture is againstirred at ambient temperature. The volatile products are removed underreduced pressure and the grayish-brown residue is dissolved in methanol(364 ml). The solution is heated at ˜50° C. until complete conversion isobtained, (determined by HPLC after approximately 11 h). The darkreaction mixture is concentrated under reduced pressure until theproduct begins to crystallize. The precipitated product is isolated byfiltration and washed with methanol (0.2 l). The crude product isrecrystallized by suspending in diethyl ether (0.6 l) and refluxing,while heptane (1.8 l) is added and the heating is continued so as tomaintain the mixture at reflux for a further 15 min. The mixture iscooled to ambient temperature and the product is isolated by filtration.The product is dried, to give the compound (2) (31.70 g, 63%) in theform of a light gray powder.

¹H NMR (300 MHz, CDCl₃): 2.21 (s, two CH₃), 2.43 (t, two CH₂), 2.68 (t,two CH₂), 3.50 (s, two CH₃), 3.89 (s, CH₂), 5.17 (s, two CH₂), 7.20 (m,10H), 9.00 (broad singlet, two NH).

Preparation 8

Preparation of the Pyrromethane of Formula (1):

A low-pressure hydrogenation apparatus is loaded with the compound (2)(30.7 g, 49.9 mmol), THF (400 ml) and catalyst Pd/C at 10% (1.5 g,A027). The hydrogenation is carried out at ambient temperature under ahydrogen pressure atmosphere in 3 h. 2N ammonia 2N (0.1 l) is added tothe reaction mixture and the catalyst is removed by filtration. Thefiltrate is adjusted to pH˜7 by adding acetic acid (60 ml). The solventis removed under reduced pressure. The precipitated product is isolatedby filtration, to give, after drying, the compound (1) (21.7 g,quantitative) in the form of a white powder.

¹H NMR (300 MHz, DMSO-D6): 2.18 (s, two CH₃), 2.20 (t, two CH₂), 2.59(t, two CH₂), 3.60 (s, two CH₃), 3.82 (s, CH₂).

Preparation 9

Preparation of the Pyrromethane of Formula (II.1):

A 1 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withtrifluoroacetic acid (190 ml) and cooled to 0° C. The compound (1) (20.0g, 46.0 mmol) is added in small portions in 10 min at 0° C. The mixtureis stirred again at 0° C. for 1 h. The conversion is followed by HPLC.Trimethyl ortho-formate (57 ml) is added dropwise in 30 min, while thetemperature is maintained at between 0 and 5° C. The reaction mixture isstirred for a further 1 h at 0° C. and then poured into water (1.7 l).The mixture is stirred vigorously for 10 min. The precipitated crudeproduct is isolated by filtration and washed with water (0.3 l) in theform of an orange powder. The crude product is triturated in ethanol(0.2 l) and ammonia (0.4 l). The mixture is stirred for 30 min atambient temperature and the product is isolated by filtration and washedwith water (0.3 l) in the form of a dark yellow powder. The product isrefluxed in methanol (0.4 l) for 10 min. The mixture is cooled toambient temperature and the product is isolated by filtration and washedwith cold methanol (0.1 l). The product is dried under reduced pressure,to give the compound (II.1) (15.30 g, 83%) in the form of a light yellowpowder.

¹H NMR (300 MHz, CDCl₃): 2.30 (s, two CH₃), 2.53 (t, two CH₂), 2.81 (t,two CH₂), 3.72 (s, two CH₃), 4.06 (s, CH₂), 9.46 (s, two CHO), 10.43(broad singlet, two NH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 2 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 6.78 min (>96%)

Preparation 10

Preparation of the Pyrromethane of Formula (V.1):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (VII.1) (50.0 g, 194.4 mmol), the compound (VI.1) (51.3 g,155.6 mmol) and dichloroethane (1.1 l). The mixture is heated to 40° C.,to give an orangey-red solution. HBF₄ etherate (2.35 ml (54%), 9.3 mmol)is added and the mixture is heated rapidly to 90° C. The conversion isfollowed by HPLC. After 1 h, the mixture is cooled rapidly to ambienttemperature and poured into a saturated bicarbonate solution (0.5 l).The layers are separated and the aqueous phase is extracted withdichloroethane (0.5 l). The combined organic extracts are dried(Na₂SO₄), filtered, stirred with Norrit C (2 g), filtered and completelyconcentrated under reduced pressure, to give a sticky brown syrup (96.5g). The crude product is dissolved in methanol (0.3 l), concentratedunder reduced pressure and again dissolved in methanol (150 ml).Germination crystals are added and the mixture is left to stand for 15 hat ambient temperature while the product crystallizes. The supernatantis removed and the crystals (fraction K1, 34.3 g) are washed withmethanol. The combined methanol fractions are completely concentratedunder reduced pressure and chromatographed on silica (420 g), elutionbeing carried out with hexane/ethyl acetate (2/1). The fractionscontaining the product are combined and concentrated under reducedpressure. The product is recrystallized as above in methanol, to give afraction K2 (16.7 g). The supernatant is again chromatographed on silica(400 g), elution being carried out with hexane/ethyl acetate (2/1). Thefractions containing the product are combined and concentrated underreduced pressure. The product is recrystallized as above from methanol,to give a fraction K3 (3.7 g). The product fractions (K1-K3) arecombined, dissolved in toluene and completely concentrated under reducedpressure. After drying under reduced pressure at 50° C. for 1 h, thecompound (V.1) (54.7 g, 68%) is recovered in the form of off-whitecrystals.

¹H NMR (300 MHz, CDCl₃): 2.09 (2.09, CH₃), 2.49 (s, CH₃), 2.50 (s, CH₃),2.58 (s, CH₃), 4.04 (s, CH₂), 5.27 (s, CH₂), 5.29 (s, CH₂), 7.35 (m,10H), 10.5 (broad singlet, NH).

Preparation 11

Preparation of the Pyrromethane of Formula (IV.1):

A low-pressure hydrogenation apparatus is loaded with the compound (V.1)(54.3 g, 103.1 mmol), tetrahydrofuran (700 ml), triethylamine (20.8 g,206.2 mmol) and catalyst Pd/C at 10% (2.75 g). The hydrogenation iscarried out at ambient temperature under a hydrogen pressure atmospherein 3 h. The catalyst is removed by filtration. The filtrate isconcentrated under reduced pressure. After drying under reduced pressureat 45° C. for 0.5 h, the compound (IV.1) (54.7 g, quantitative) isrecovered in the form of an off-white foam, in the form of amonotriethylamine salt containing residual amounts of toluene and ofTHF.

¹H NMR (300 MHz, DMSO-D6): 1.97 (s, CH₃), 2.38 (s, CH₃), 2.52 (s, twoCH₃), 4.14 (s, CH₂).

Preparation 12

Preparation of the Pyrromethane of Formula (IIIa):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with solidNaHCO₃ (55.6 g, 662.0 mmol), water (900 ml) and ethanol (300 ml). Asolution of the compound (IV.1) (54.3 g, 101.9 mmol) in ethanol (300 ml)is added. A solution of iodine (64.7 g, 254.9 mmol) in ethanol (400 ml)is added, at ambient temperature, to give a brown heterogeneous mixture.A certain amount of foaming and a reduced exothermia are observed. Theconversion is followed by HPLC. The reaction mixture is stirred again atambient temperature for 5 h. The reaction mixture is diluted with water(0.1 l) and the precipitated product is isolated by filtration. Theprecipitate is washed with water (3×0.1 l), ethanol (2×0.1 l) and ether(2×0.1 l). After drying of the crystals of product under reducedpressure at 60° C., the compound (III.a) (48.1 g, 92%) is recovered inthe form of light red crystals.

¹H NMR (300 MHz, DMSO-D₆): 2.06 (s, CH₃), 2.15 (s, CH₃), 2.33 (s, CH₃),4.08 (s, CH₂).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 2 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 8.13 min (>92%)

Preparation 13

Preparation of the Porphyrin of Formula (Ia.1):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded withacetic acid anhydride (290 ml), acetic acid (1.8 l) andtrifluoromethanesulfonic acid (4.95 ml, 56.77 mmol). A substantiallyhomogeneous solution of the compound (II.1) (12.00 g, 29.82 mmol) and ofthe compound (IIIa) (14.48 g, 28.40 mmol) in acetic acid (400 ml) isadded, at ambient temperature, in 5 min, which produces a blood redsolution. No exothermia is observed. The mixture is stirred again atambient temperature for 1 h, with the formation of a certainprecipitate. The conversion is followed by HPLC. A solution of NaOAc(9.4 g) in acetic acid (100 ml) is added, to give a dark brown solution.After 10 min, the volatile products are removed under reduced pressureand dried under reduced pressure for 1.5 h at 50° C. The dark residue istaken up in dichloromethane (300 ml), and water (500 ml) withoutvigorous mixing. The organic layer is separated and the aqueous phase isextracted with dichloromethane (0.3 l). The combined organic phase isdried (Na₂SO₄), filtered and concentrated, to give a black crystallineproduct (31.3 g). The mixture is dissolved in dichloromethane andapplied to a column of silica gel (1 kg) covered withdichloromethane/acetone (95/5). The product is eluted with a gradient of95/5 to 90/10. The fractions contained in the product are combined andcompletely concentrated under reduced pressure. The compound (Ia.1)(9.97 g, 55%) is recovered in the form of violet-black crystals.

¹H NMR (300 MHz, CDCl₃): 3.15 (two t, two CH₂), 3.17 (s, CH₃), 3.25 (s,CH₃), 3.39 (s, CH₃), 3.50 (s, CH₃), 3.60 (s, CH₃), 3.64 (s, CH₃), 3.65(s, CH₃), 3.71 (s, CH₃), 4.22 (two t, two CH₂), 9.50 (s, CH), 9.59 (s,CH), 10.43 (s, CH), 10.46 (s, CH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 3 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 11.66 min (>93%)

Preparation 14

Preparation of the Porphyrin of Formula (Ib.1):

A 1 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (Ia.1) (9.86 g, 15.84 mmol), dichloromethane (500 ml) andmethanol (24 ml). NaBH₄ (3.00 g, 79.32 mmol) is added portionwise to thereddish-brown mixture. A certain foaming is observed. The reaction isclosely followed by HPLC. After 80 min, the mixture is poured into amixture of water (500 ml) and 4N HCl (80 ml). Gas is seen to be givenoff. The mixture is neutralized by adding solid NaHCO₃. The layers areseparated and the aqueous phase is extracted with dichloromethane (2×300ml). The combined organic extracts are dried (Na₂SO₄), filtered andconcentrated under reduced pressure. After drying under reduced pressureat 50° C. for 0.5 h, the compound (Ib.1) in the form of a mixture of twostereoisomers (9.58 g, 96%) is recovered in the form of violet-blackcrystals.

¹H NMR (300 MHz, CDCl₃): 1.92 (m, 6H, two CH₃), 3.16 (m, 4H, two CH₂),3.28, 3.30, 3.33 and 3.35 (4 s, 6H, two CH₃), 3.43 (s, 6H, two CH₃),3.66 (s, 6H, two CH₃), 4.20 (m, 4H, two CH₂), 6.05 (m, 2H, two CH),9.73, 9.74, 9.75, 9.76, 10.00, 10.02, 10.08 and 10.10 (8 s, total 4H,four CH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 3 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 7.90 min, 51% and 8.01 min, 49%

Preparation 15

Preparation of the Porphyrin of Formula (Ic.1):

A 1 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (Ib.1) (9.48 g, 15.12 mmol) and DMF (400 ml) and the mixture isdegassed with argon. Benzoyl chloride (45.0 ml, 387.9 mmol) is added andthe mixture is rapidly heated to 100° C. The mixture is stirred again at100° C. for 1 h. The conversion is followed by HPLC. The reactionmixture is cooled rapidly and the volatile products are removed underreduced pressure. The residue is dissolved in dichloromethane (0.3 l)and stirred vigorously with a water/methanol (0.3 l) mixture. The layersare separated and the aqueous phase is extracted with dichloromethane(2×0.2 l). The combined organic extracts are washed with bicarbonate(0.3 l), dried (Na₂SO₄) and filtered. The filtrate is treated withsilica (20 g) and filtered. Methanol (50 ml) is added and the mixture isthen concentrated under reduced pressure, while crystallization takesplace toward the end, to give a violet-black product (20 g). The productis triturated with methanol at 50° C. for 0.5 h. After cooling toambient temperature, chloroform (2 ml) is added and the product isisolated by filtration. After drying under reduced pressure at 50° C.for 15 h, the compound (Ic.1) (6.34 g, 77%) is recovered in the form ofshiny violet-black crystals.

¹H NMR (300 MHz, CDCl₃): 3.23 (t, two CH₃), 3.52 (s, CH₃), 3.54 (s,CH₃), 3.58 (s, CH₃), 3.64 (s, CH₃), 3.64 (s, CH₃), 3.65 (s, CH₃), 3.66(s, CH₃), 4.32 (t, two CH₂), 6.11-6.34 (m, 4H, two CH₂═), 8.10-8.23 (m,2H, two CH═), 9.85, 9.86, 9.97 and 9.98 (4 s, 4CH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents with 0.1% of TFA: acetonitrile (ACN)-water: from 1 to 100% ofACN for 10 min, then 6 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 1 mg/1.5 ml of ACN

Rt: 12.43 min (>97%)

Preparation 16

Preparation of the Porphyrin of Formula (IC.2, 2Na):

A 2.5 l Keller round-bottomed flask equipped with a reflux condenser, athermometer, a dropping funnel and an argon conduit is loaded with thecompound (Ic.1) (6.30 g, 10.67 mmol) and dichloromethane (200 ml). Theproduct is dissolved by heating to 40° C. At 40° C., methanol (400 ml)followed by 4N NaOH (200 ml) are successively added. The formation of aprecipitate is observed. The mixture is refluxed. The conversion isfollowed by HPLC. The organic volatile products are removed underreduced pressure. The suspension is filtered through a glass fiberfilter. The product is washed with water (3×0.1 l), methanol (3×30 ml)and diethyl ether (2×30 ml). After drying under reduced pressure at 70°C. for 2 h, then at 40° C. for 15 h, the compound (Ic.2, 2Na) (6.06 g,94%) is recovered in the form of a violet-black solid product.

¹H NMR (300 MHz, TFA-D₁): 3.45 (two t, two CH₂), 3.82 (s, CH₃), 3.85 (s,CH₃), 3.88 (s, CH₃), 3.91 (s, CH₃), 4.73 (two t, two CH₂), 6.43-6.70 (m,4H, two CH₂═), 8.28-8.40 (m, 2H, two CH═), 11.08, 11.11, 11.15, and11.27 (4 s, 4CH).

RP-HPLC:

HP Hypersil BDS-C C18, 125×4 mm, 25° C.

Solvents: acetonitrile (ACN) with 0.1% of TFA-water with 0.1% of TFA:from 1 to 100% of ACN for 10 min, then 6 min with 100% of ACN

Flow rate: 1 ml/min, detection at 220 nm

Sample: 0.1 mg/1.5 ml of AcOH/DMF

Rt: 9.85 min (>98%)

Elemental Analysis

Theory for C34•H32•N4•04•Na₂ (MW 606.63) Result C 67.32 +/− 0.3% m/m64.91% m/m  H 5.32 +/− 0.3% m/m 5.38% m/m N 9.24 +/− 0.3% m/m 8.94% m/mWater 3.56% m/m Na 7.58 m/m 7.15% m/m

With measurements adjusted after the addition of 1.24 mol of water(amount of water measured by Karl-Fisher titration) per mole of product.

Theory for C34•H32•N4•04•Na2•1.24 H₂O (MW 636.54) Result C 64.93 +/−0.3% m/m 64.91% m/m  H 5.28 +/− 0.3% m/m 5.38% m/m N 8.91 +/− 0.3% m/m8.94% m/m Water 3.56 m/m 3.56% m/m Na 7.31 m/m 7.15% m/m

1. A process for preparing a porphyrin of formula (I), optionally in theform of a salt:

in which: R is a hydrogen, —CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃, or—CH₂CH₂COOR′a, wherein R′a is hydrogen, methyl, ethyl, n-propyl, ori-propyl, R′ is hydrogen or R′b wherein R′b is methyl, ethyl, n-propylor i-propyl, the method comprising: condensing, in an acidic medium, adipyrromethane of formula (II)

in which R′b is as defined above for (I), with a dipyrromethane offormula (III):

in which R″ is selected from hydrogen, —CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃,—C(O)CH₃, —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃ and —CH₂CH₂Cl or —CH₂CH₂COOR′a,wherein R′a is hydrogen, methyl, ethyl, n-propyl, or i-propyl, and R″ iseither identical to R as defined above for (I) or is a precursor of R,so as to form the porphyrin of formula (I′):

in which R″ and R′b are as defined above for (II) and (III), and, whenR″ is a precursor of R, further comprising converting R″ to R, and whenR′═H, further comprising eliminating R′b so as to form —COOH moieties,optionally in the form of a salt.
 2. The process as claimed in claim 1,wherein in the compound of formula (I), R is hydrogen, —CH₂—CH₃,—CH(OH)CH₃, —C(O)CH₃ and —CH₂CH₂COOR′a, wherein R′a is hydrogen, methyl,ethyl, n-propyl or i-propyl group.
 3. The process as claimed in claim 1,wherein in the compound of formula (I) R is a —CH═CH₂ group, the methodcomprising: condensing, in an acidic medium, a dipyrromethane of formula(II):

in which R′b is as defined above for (I), with a dipyrromethane offormula (III):

in which R″ is —CH₂CH₂OH, —CH₂CH₂Cl, —CH₂CH₂OC(O)CH₃, —CH(OH)CH₃ or—C(O)CH₃, followed by conversion of the groups R″ to R, and when R′═H,further comprising eliminating the groups R′b so as to form —COOHmoieties, optionally in the form of a salt.
 4. The process as claimed inclaim 3, wherein R″ is —CH(OH)CH₃ or —C(O)CH₃.
 5. The process as claimedin claim 1, wherein the compound of formula (I) is a compound of formula(IA):

in which R′ is as defined for (I), or a salt thereof, by coupling thepyrromethane of formula (II):

in which R′b is as defined above for (I), with the dipyrromethane offormula (IIIa):

and, when R′ is a hydrogen atom, further comprising eliminating the R′bmoieties by hydrolysis, or, optionally, when the compound (IA) to beformed is in the form of a salt, further comprising eliminating R′bmoieties by saponification.
 6. The process as claimed in claim 5,wherein R′b is methyl.
 7. The process as claimed in claim 1, wherein thecompound of formula (I) is a compound of formula (IB):

in which R′ is as defined for (I), or a salt thereof, by coupling apyrromethane of formula (II):

in which R′b is as defined above for (I), with a dipyrromethane offormula (IIIa):

so as to form the compound of formula (Ia):

in which R′b is as defined for (I), followed by reduction of the—C(O)CH₃ moieties to —CH(OH)CH₃, and, when R′ is a hydrogen atom,further comprising eliminating the R′b moieties by hydrolysis, or, whenthe compound (IB) to be formed is in the form of a salt, furthercomprising eliminating R′b moieties by saponification.
 8. The process asclaimed in claim 7, wherein the reduction of the —C(O)CH₃ moieties iscarried out in the presence of a hydride.
 9. The process as claimed inclaim 8, wherein the reduction of the —C(O)CH₃ moieties is carried outin dichloromethane in the presence of methanol.
 10. The process asclaimed in claim 3, wherein the compound of formula (I) is a compound offormula (IC):

in which R′ is as defined for (I), or a salt thereof, by coupling apyrromethane of formula (II):

in which R′b is as defined above for (I), with a dipyrromethane offormula (IIIa):

so as to form the compound of formula (Ia):

in which R′b is as defined for (I), followed: by reducing the —C(O)CH₃moieties, resulting in the formation of the porphyrin of formula (Ib):

in which R′b is as defined for (I), followed by converting the—CH(OH)CH₃ groups to —CH═CH₂ groups, and, when R′ is a hydrogen atom,eliminating R′b moieties by hydrolysis, or, when the compound (IC) to beformed is in the form of a salt, further comprising eliminating R′bmoieties by saponification.
 11. The process as claimed in claim 10,wherein the reaction that converts the —CH(OH)CH₃ groups to the —CH═CH₂groups is carried out in the presence of an acid halide.
 12. The processas claimed in claim 11, wherein the reaction that converts the—CH(OH)CH₃ groups to —CH═CH₂ groups is carried out in an aprotic polarsolvent.
 13. The process as claimed in one of claims 10 to 12, whereinthe reduction of the —C(O)CH₃ moieties is carried out in the presence ofa hydride.
 14. The process as claimed in claim 13, wherein the reductionof the —C(O)CH₃ moieties is carried out in dichloromethane in thepresence of methanol.
 15. The process as claimed in claim 14, whereinR′b is a methyl group.
 16. The process as claimed in claim 15 whereinthe compound of formula (I) is protoporphyrin (IX) in the form of thesodium salt of formula (IC.2, 2Na):

further comprising saponifying the compound of formula (Ic):


17. The process as claimed in claim 16, wherein the saponification iscarried out in dichloromethane at reflux.
 18. The process as claimed inclaim 1, wherein the condensation reaction between the two pyrromethanes(II) and (III) is carried out in the presence of an acid selected fromthe carboxylic acids, trifluoroacetic acid, hydrochloric acid,trichloromethanesulfonic acid, methanesulfonic acid,trifluoromethanesulfonic acid, tetrafluoroboric acid, hydrobromic acidand hydriodic acid.
 19. The process as claimed in claim 18, wherein theacid is trifluoroacetic acid or trichloromethanesulfonic acid.
 20. Theprocess as claimed in claim 18, wherein the condensation reactionbetween the two pyrromethanes (II) and (III) is carried out in thepresence of a desiccating agent.
 21. The process as claimed in claim 20,wherein the desiccating agent is selected from anhydrides, molecularsieves and sulfuric acid.
 22. The process as claimed in claim 21,wherein the desiccating agent is acetic anhydride.
 23. The process asclaimed in claim 22, wherein the acetic anhydride is present in anexcess of at least 10 mol equivalents relative to the pyrromethane (II).24. The process as claimed in claim 18, wherein the condensation iscarried out with substantially one mol equivalent or a slight excess ofpyrromethane (II), relative to the pyrromethane (III).
 25. The processas claimed in claim 18, wherein the condensation reaction between thetwo pyrromethanes (II) and (III) is carried out at a temperature of from10 to 50° C. in a protic solvent.
 26. A process for preparing a metalcomplex of porphyrin of formula (I), optionally in the form of a salt:

in which: R is hydrogen, —CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ or—CH₂CH₂COOR′a, with R′a being hydrogen, methyl, ethyl, n-propyl ori-propyl, R′ is hydrogen, or R′b, wherein R′b is methyl, ethyl, n-propylor i-propyl, the method comprising complexing the metal, the salt of themetal or the hydroxide of metal with the product of the condensation ofa compound of formula (II):

in which R′b is as defined above for (I), with a dipyrromethane offormula (III):

in which R″ is R as defined above for (I) or when R″ is other than R itis selected from, —C(O)CH₃, —CH(OH)CH₃, —CH₂CH₂OH, —CH₂CH₂OC(O)CH₃ and—CH₂CH₂Cl groups.
 27. The process as claimed in claim 26, wherein themetal, the metal component of the salt of the metal, or the metalcomponent of the hydroxide of metal is selected from iron, gallium,nickel, zinc, palladium, cobalt, calcium and magnesium.
 28. The processas claimed in claim 27, wherein the complexing is carried out, in afinal step, on a porphyrin of formula (I), optionally in the form of asalt.
 29. The process as claimed in claim 27 or 28, wherein the finalproduct is heme, hemin or hematin.
 30. A pyrromethane of formula (III):

in which R″ is hydrogen, —CH═CH₂, —CH₂—CH₃, —CH(OH)CH₃, —C(O)CH₃ or—CH₂CH₂COOR′a, with R′a being hydrogen, methyl, ethyl, n-propyl ori-propyl.
 31. The pyrromethane as claimed in claim 30, in which R″ is aprecursor of —CH═CH₂ selected from the group consisting ofCH₂CH₂OC(O)CH₃, —CH₂CH₂OH, —CH₂CH₂Cl, —CH(OH)CH₃ and —C(O)CH₃.
 32. Acompound selected from the compounds of formulae (VIIa), (Va) and (IVa):


33. A porphyrin of formula (I):

in which —R is a —CH(OH)CH₃, —C(O)CH₃, or —CH₂CH₂COOR′a, wherein R′a ishydrogen, methyl, ethyl, n-propyl, or i-propyl, and R′ is hydrogen orR′b wherein R′b is methyl, ethyl, n-propyl or i-propyl.